Allow users access to a BDC-application

I have created a business data catalog application that works well when I am logged in being the Administrator. But how can I allow users to view information from the BDC?

I have added users from Active Directory via the Business Data Catalog Permissions, I have imported a permissions.xml-file, I placed users to a group that I gave rights in the SQL-server to view data... but all the time I get an error: "Unable to connect to..." as soon as I log in as a user.

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